Dewaxing of mineral oils



Patented Nov. 28, 1939 PATENT OFFICE Texas Company, New York, N. Y., a corporation 7 v of Delaware N Drawing. Application June 25, 1938,

- Serial No. 215,877

'5 Claims.

. 'I'his invention relates to the dewaxing of hydrocarbon oil and particularly to the separation of wax from a mineral lubricating oil.

The invention contemplates the separation of '5 Wax from such a wax-bearing oil by the employment of a-wax crystal modifying material to facilitate dewaxing by filtration, centrifuging or wold-settling. More particularly, the invention contemplates separating the wax from the oil '10 in the presence of a wax crystal modifying material comprising a chromium. soap of a carboxylic acid containing around 10 to 30 carbon atoms. The acids contemplated may be stearic, palmitic, ol-eic, linoleic, behenic and 'cerotic acid.

' Other acids are naphthenic acids and mixtures of naphthenic acid such as obtained in the refining of petroleum. Still other acids that may be employed are abietic, ricinoleic, as well as oxidationproductsigof paraffin wax.

It is also contemplated using the chromium soap of these acids alone or in conjunction with a small amount of montan wax. While crude montan wax has been found particularly effective, it is contemplated that the active ingre- 2 clients thereof may be employed.

I have discovered that chromium soap such as chromium stearate, for example, is unique in its properties as a wax crystal modifying material, particularly since it is highly effective as such in the presence of a wet solvent. By wet solvent is meant a dewaxing solvent containing a small amount of water. The chromium soap in this respect is in marked contrast with other metallic soaps It has been found from actual experience that while the previously known metallic soaps are effective in the presence of a dry or anyhydrous dewaxing solvent, they lose a substantial part of their effectiveness in the presence of a wet solvent.

ploying dewaxing solvents it is found difficult, if not economically impossible, to maintain the solvent of the system in an anhydrous condition, the solvent frequently containing as much as /2% or more of water.

Chromium stearate, for example, retains its full effectiveness in the presence of wet solvent, therebypermitting realization of a high yield of dewaxed oil, denser or more compact wax cake,

a higher percentage of paraffin in the slack Wax,

and a slack wax of higher melting point.

The chromium compound, therefore, possesses an unexpectedadvantage over the more commonly known wax crystal modifying materials.

While the modifying material is employed in and toluol, and the like.

In commercial dewaxing plants emv m: conjunction with a dewaxing solvent or solvent mixture, various-solvents-can be used for this purpose, including the well-known and conventional dewaxing solvents and solvent mixtures. Very satisfactory results are secured by the use,;,- 5 of a mixture of a wax anti-solvent and an oil solvent, such as amixture of, acetone and benzol, methyl ethyl ketone and benzol, methyl ethyl ketone and isopropyl ether, acetone with ben zol In the case of methyl ethyl ketone-benzolfor methyl ethyl ketone-isopropyl ether, generally a proportion of about 40 to methyl ethyl ketone to 60 to 40% benzol or isopropyl ether is satisfactory. l The oil to be dewaxed is diluted with the de- Waxingsolvent or solvent mixture. generallyin the dilution'ratioof about Zparts of solvent to one of oil up to about four or five partsof solratio may be employed in certain instances.

The soap, or the soap and montan wax, may be dissolved in a small proportion of the lubricating oil at elevated temperatures up to about 300 F. to form a concentrate thereof. This con- 25 centrate is then added to the diluted Wax-bearing oil charge at a lower'temperature of the order of 120 F.

In order to realize the maximum effectiveness of the wax crystal modifying material it is ad- 30 vantageous to incorporate the material in the mixture of wax-bearing oil and dewaxing solvent and heat the resulting mixture to a temperature substantially above the temperature of complete solution of the wax and oil in the solvent. The 35 perature of the order of 10 or 15 F. to pre- 40 cipitate the wax. The precipitated wax is then removed from the cold mixture advantageously by filtration in a continuous rotary filter. The dewaxed filtrate is then stripped to remove the solvent and thus obtain a dewaxed oil having a 45 pour test corresponding substantially to the temperature at which the cold mixture was filtered.

In the following examples a solvent refined wax distillate havingan A. P. I. gravity of 27.7, a Saybolt Universal viscosity of 86.9 at 210 F., a 50 pour test of 115, and a parafiln content of around 12%, was dewaxed. The solvent consisted of a mixture of 40% methyl ethyl ketone and 60% benzol, and contained /2% water. In each case grams of oil were mixed with the solvent in 55 Run Run Run No. 1 N0. 2 N0. 3

Percent chromium stearate 0.0 0.25 0.25 Percent montan waxl l 0. 0. O 0. 05 Weight of oil in grams... 72 8 86 Percent yield of dewaxed 0 65. 4 76. 3 78. 2 Filter cake thickness in inche Zia Weight of cake in grams 96 55 46 Weight of slack wax in grams W 22 22 As indicated by the foregoing data, when dewaxing in the absence of the modifying material, a yield of 65.4% dewaxed oil was obtained. In the presence of 0.25% chromium stearate (by weight of the wax-bearing oil) the yield was increased to 76.3%. When the soap was used in conjunction with montan wax the yield was somewhat further increased to 78.2%. The presence of soap in the second run reduced the weight of the wax cake to grams, as compared with grams in the absence of any modifying material. The weight of the wax cake was further reduced to 46 grams in the third run when using both soap and montan wax. Thus, the chromium soap, either alone or in conjunction with the montan wax, gave very greatly improved results. The montan wax appears to exert its beneficial action upon the higher melting point constituents of the wax, while the soap exerts its maximum efiect upon those constituents of the wax which are of lower melting point and precipitated at lower temperatures.

The amount of modifying material employed is usually less than 1% by weight of the waxbearing oil. Satisfactory results are usually secured when using about 0.15 to 0.50% of soap and about 0.02 to 0.25% of the montan wax.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of dewaxing a mixture of waxbearing oil and dewaxing solvent containing a small amount of water which comprises incorporating in the mixture a small amount of a chromium soap of a high-er fatty acid, chilling the mixture to precipitate wax, and separating the precipitated wax from the chilled mixture.

2. The method according to claim 1, in which the chromium soap comprises a soap of a carboxylic acid containing around 10 to 30 carbon atoms.

3. The method according to claim 1, in which the chromium soap comprises chromium stearate.

4. The method according to claim 1, in which the chromium soap comprises a chromium soap of oxidized paraffin wax.

5. The method of dewaxing a mixture of waxbearing oil and dewaxing solvent containing a small amount of water which comprises incorporating in the mixture a small proportion of montan wax and a chromium soap of a higher fatty acid, chilling the mixture to precipitate Wax, and separating the precipitated wax from the chilled mixture.

LEON W. COOK. 

